Analysis Of The Influence On Reverse Construction Method Of Self-underground Structure

With the rapid changes in the city,the rapid expansion of population and increasingly scarce land resources,underground space is being developed and utilized,the size of the foundation pit project is also deeper.Deep foundation pit engineering often appears in the bustling downtown,not only its own internal structure and the geological conditions in which complex,the surrounding environment is also very complex,there are a lot of buildings,traffic roads and underground pipelines.So the requirements of the excavation of the pit more stringent,and further increase the difficulty of construction,construction not only to ensure that the deformation of the foundation pit and force to meet the conditions,but also to control the surrounding environment such as the surface,buildings,traffic roads,underground pipelines and other changes in the impact caused by the force.This makes the engineers tend to use the reverse approach for foundation pit excavation,because it is more mature development and it has many advantages,its design and construction in many practical projects have been successfully used and accumulated a lot of valuable experience.But the current practice in the Hefei area less practice,also belong the initial stage.Therefore,this paper will combine a large and ultra-deep foundation pit in Hefei area,give a comprehensive and concrete analysis of the reverse construction method of excavation on the underground structure of the impact of the law,for the future Hefei similar projects to provide a reference.(1)This paper summarizes the principles,classification and characteristics of the reverse approach,and summarizes the application development and the current research situation of the reverse practice at home and abroad,finds that there are still many problems to be solved in the construction and design of the current reverse method,this is also the details of the study in this note.(2)The research of this paper is based on the construction of super large and deep foundation pit reverse construction method——the basement of Hefei New Transportation Building.Summarizes the basic situation of the project,such as the scale of the project,the way of excavation and the underground structure;the engineering and hydrological aspects of the project site of the geological conditions were described in detail;lists the surrounding environment that may interact with the foundation pit include buildings,traffic roads and underground pipelines.At the same time,combined with the above three factors,the paper analyzes the difficulties and possible problems in the inverse excavation processof the foundation pit,thus the deformation and force analysis of the self-underground structure as the research focus of this paper.(3)Numerical simulation is the main research method of this paper,so the first of the selected finite element software Midas/GTS NX on its advantages,areas of application and operational procedures were outlined;and then summed up the realization of finite element method and the constitutive model of soil and other related theoretical knowledge;finally,the numerical simulation on inverse excavation process through combining with the actual foundation pit construction and research emphasis,which gives the three important stages of the numerical simulation establishment process,including the basic assumptions of the model,the model’s build data,and the simulation’s construction steps.Ultimately,the influence of inverse excavation on the surface subsidence,the horizontal deformation of the connected wall and the vertical displacement of the vertical column are discussed in detail by numerical calculation results and field monitoring data,and the concrete conclusions are drawn.In addition,the calculated results are compared with the measured results,coupled with domestic and foreign scholars to study the empirical theory and traditional classical curve comparison,analyze the causes of the error,so as to verify the rationality and feasibility of the model,and enhance the persuasiveness of the analysis of the horizontal floor deformation and force by numerical simulation.(4)It is also the innovation and emphasis of this paper to study the influence of the foundation pit reverse excavation on the deformation and stress of the horizontal floor.Using the form,the graph and the form of the cloud,from different levels floor and the same floor at different locations,the comprehensive and specific study summarizes the deformation law of the horizontal floor;from the perspective of bending moment and shear force of the floor,the qualitative analysis summarizes the force law of the horizontal floor.And find out the unfavorable floor,location and status of the floor during the inverse excavation of the foundation pit,and provide reference for the prevention and control in the construction.